Automotive keyless entry systems, especially Passive Entry/Passive Start (PEPS) systems, have been facing a threat referred to as a “relay attack”, which permits a vehicle to be opened and possibly stolen without the owner's awareness.
The relay attack requires two thieves working in cooperation with each other. Each of the two thieves carries a device (referred to as an attack kit) capable of receiving a signal from either the vehicle or the vehicle's keyfob and forwarding the received signal to the other thief after amplifying the signal. In one scenario, the thieves follow the vehicle and its driver. The driver stops at, for example, a store or a restaurant. Thief-1 stands adjacent to the parked vehicle and thief-2 follows and stands next to the owner of the vehicle (which may be inside the store or restaurant). Thief-1 pushes a button on the vehicle's door to initiate a door unlock operation, which normally requires a valid keyfob to be within a foot or two of the door. Upon pressing the door button, the vehicle broadcasts a wireless signal intended for reception by a valid, nearby keyfob.
The wireless device carried by thief-1 picks up the wireless signal being broadcast by the vehicle and relays the signal (albeit possibly at a different power level or frequency) through thief-1's attack kit to the attack kit of thief-2. Upon receiving the signal from thief-1, thief-2 replicates the signal in the format commensurate with the keyfob and transmits the replicated keyfob-compliant signal to the keyfob carried by the vehicle's owner (which presumably is within sufficient range of thief-2); thereby waking up the keyfob. The keyfob which receives the wireless signal and cannot distinguish thief-2's attack kit from the vehicle itself considers the attack kit carried by thief-2 as the vehicle and, as it is configured to do, transmits a wireless response signal to authenticate the keyfob to the vehicle. This response signal is then received by the attack kit of thief-2 which relayes the signal back to the attack kit of thief-1. Thief-1 receives the response and replicates a wireless signal compatible with the vehicle. The vehicle's wireless communication system cannot distinguish a wireless signal from the attack kit of thief-1 from the keyfob itself and performs the designated operation (e.g., door unlock).